The B-Grip Travel Kit allows you to attach your camera directly onto your backpack shoulder strap. If you attempted that trick with the B-Grip quick-release system but without this Travel Kit, you'd have a horizontally oriented DSLR lens knocking against your swinging arm as you hike.
The Travel Kit allows you to attach the B-Grip and your camera to your backpack strap with the proper orientation lens pointed down. The most comfortable way of carrying the camera when traveling with a backpack. Whether it's a backpack strap or another closed-circuit strap, the Travel Kit lets you mount the camera/lens/B-Grip parallel to the strap rather than perpendicular, as you typically want with a belt (and as the B-Grip belt holster on its own enables). By using the Travel Kit to mount it to your backpack strap, you can keep your B-Grip-mounted DSLR secured to your chest and ready to shoot.